kossel mini - belt slipping off flanged bearings toward center of vertices

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rrhb

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Apr 17, 2014, 12:13:56 AM4/17/14
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I seem to have a recurring issue with the belt slipping forward toward the center off the top of one or more of the three flanged bearings.  The flange on the 623 bearing just doesn't seem wide enough to keep the belt from touching the inside of the top vertex.

Anyone else seeing this?  

Fixes?

-rrhb

Glenn Goodman

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Apr 17, 2014, 12:27:25 AM4/17/14
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rrhb,

I do not have a Kossel mini however it sounds as though you have an alignment issue with one of the pulleys.  Either one is off center of the other one or your pulley are at an angle to each other.  If everything is aligned then the belt should stay exactly where it is and not wander off.

Here is a quick test to determine whats off...

Center the belt on one of the pulleys and then tighten it up.  Check to see where it is on the second pulley.  Try and center the second pulley as best as possible.  Having one slightly off center of the other shouldn't be an issue as long as the belt isnt rubbing.  Now spin the belt so the pulley fully rotates 10 to 20 times and watch the belts for any side movement (walking towards one end or the other).  

If the belts stay where they were aligned then it is a simple matter of centering the pulleys.  If the belt tends to walk towards the flange then you have an alignment issue.  This means that one of the pulleys is at an angle to the other.  Check to see if the motor is tight or has debris between the mount and motor, check the idler side for any movement or miss alignment / bent parts etc...

Doug LaRue

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Apr 17, 2014, 1:44:29 AM4/17/14
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Your carriage is what determines where your motor drive pulley goes on the motor shaft and where your upper idler bearings are supposed to be. If you do not have both of these lined up with where the belt is on the carriage then you're going to have belts which wander.

It would have been best to have done this before you installed the effector arms onto the carriage but basically you want to move the carrage on its mount as close to the thing you are adjusting. The belt should be straight. Once you adjust one, go to the other end and do the same. On the idler you'll have to move M3 washers around. On the pully you just loosen the set screw and slide the drive on the motor shaft. Or flip the drive on the motor shaft if needed.

Doug

Jeff Short

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Apr 17, 2014, 1:04:46 PM4/17/14
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Your top and bottom definitely need to be in alignment. Once I got mine into alignment, I used fender washers to keep the belt from moving.

M B

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Mar 28, 2020, 7:50:13 PM3/28/20
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A few years later... I'm trying to work through this same issue and not much to go on. Anyone know of any fixes? 

Edward Simpson

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Mar 28, 2020, 10:06:38 PM3/28/20
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Simplest fix is to just replace the top bearings with proper GT2 idlers, I made that change to my delta a couple years ago now.

M B

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Mar 28, 2020, 10:33:07 PM3/28/20
to Delta robot 3D printers
I was thinking about the same thing but it still won't be in perfect alignment. After some looking and a lot of thinking though, it seems that the slides/carriage that my printer came with and the frame weren't made for each other. I decided to be a bit creative and shave the inside of the bracket flat. Got through auto level without much fighting so far so fingers crossed.
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